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[Mnyb]

If you insist in a particular type of semiconductor Orchard Audio has a GaN amp that seems to perform?

This one has so many other amplifier related problems that the use of GaN is irrelevant ?

For example load dependency due to high output impedance in the treble similar to simpler and cheaper chip amps ? Not wrong but not SOTA performance and can be audible if your unlucky ?

Better class D amps has pffb

 

[goryu]

Bruno Putzey: "There is no such thing as too much feedback"
No not to an analyzer there's not. But to an ear there is if the amp still measures well with just a little local feedback and has good specs still.

Prove it.

You are not interested in facts, science, or objectivity. You are here to push your own self serving subjective agenda. You don't have the self awareness to realize you're in the wrong place.

 

[Killingbeans]

You don't have the self awareness to realize your in the wrong place.

"You're".... /grammar nazi

All I'd like to see is some solid evidence supporting the claim of feedback inherently disrupting fidelity. Not holding my breath though.

Just going "everything is subjective!" is a cop out. Well, duh. We know very well that everything is subjective. Doesn't prove anything.

 

[georgehifi]

From Nelson Pass, there are more many more quotes from other great designers.
Matti Otala, Bob Cordel, Peter Baxandall, Linsely Hood, Charles Hansen, John Curl, Doug Self, etc etc

"Instruments only measure what they were designed to measure.”

Audio distortion and feedback - Pass Labs

Audiophiles seem to revel in minor controversies – vinyl vs CD’s, tubes versus solid state, capacitor, wires, magic dots… and negative feedback. At one extreme, the position is that “feedback makes amplifiers perfect”. At the other extreme, “feedback is a … Continue reading →

www.passlabs.com

 

[kemmler3D]

All I'd like to see is some solid evidence supporting the claim of feedback inherently disrupting fidelity. Not holding my breath though.

Same

“Instruments only measure what they were designed to measure.”

Yeah, and instruments used for designing and measuring audio amplifiers are designed to measure... audio. So I'm not sure what we're supposed to be hearing that can't be seen on an oscilloscope or FFT. If there is something, that would be of truly great interest.

In your link, Pass is using the same measurements Amir uses.

Pass is correct in that IMD is objectionable and higher-order distortion is objectionable. And he even shows that apparently under some circumstances higher order distortion can be made worse via feedback. However, what we don't see is any actual amplifiers on the market showing this behavior.

He also doesn't explain the mechanism of this increase, and if you look carefully at the referenced chart from Linsley-Hood vs. his own 'experiment', you will see that the higher-order distortion drops along with the lower-order harmonics after about 15-20dB of feedback - Pass' test stops at 15dB. I don't see why he would do that.

It also bears mentioning the work he's referencing in this article is over 30 years old.

Presumably the problem Pass identified in this article is one that's (today) easy to solve, and is apparently solved in most/all commercially available amps.

 

[georgehifi]

Negative Feedback and Higher Order Harmonics
Years ago Peter Baxandall pointed out that while negative feedback reduces distortion, it creates additional higher order harmonics in the process. Others have confirmed this phenomenon experimentally and in computer simulations. I found Figure 10 on the internet, attributed to John Linsley-Hood:

 

[kemmler3D]

Negative Feedback and Higher Order Harmonics
Years ago Peter Baxandall pointed out that while negative feedback reduces distortion, it creates additional higher order harmonics in the process. Others have confirmed this phenomenon experimentally and in computer simulations. I found Figure 10 on the internet, attributed to John Linsley-Hood:

Yes, I read the article you linked. From what I have seen, the excess higher-order harmonics Pass is referring to don't show up in measurements we see of real amps on the market.

Also, again, he didn't address that it also suppresses those higher order harmonics after about 15-20dB of NFB, according to the chart in the article you linked.

Also, did you know that JLH was broadly in favor of negative feedback and even considered it necessary? I actually googled the stuff you're referencing.

 

[goryu]

I actually googled the stuff you're referencing.

Sorry to hear that. Some people just keep regurgitating yesterday's dogma, oblivious to the fact that they have been passed by as technology advances.

All we get from Mr. GaN is empty talk and hand waving. Putzeys put the feedback trope to rest several years ago and the objective performance of his amps has been proved many times over to be above and beyond. Yet, despite the fact that the performance is well documented both on this site and elsewhere, we continue to be bombarded with the fact less, proof less droolings of our subjectivist GaN investor. Where are the mods when you need them?

 

[Mnyb]

Same


Yeah, and instruments used for designing and measuring audio amplifiers are designed to measure... audio. So I'm not sure what we're supposed to be hearing that can't be seen on an oscilloscope or FFT. If there is something, that would be of truly great interest.

In your link, Pass is using the same measurements Amir uses.

Pass is correct in that IMD is objectionable and higher-order distortion is objectionable. And he even shows that apparently under some circumstances higher order distortion can be made worse via feedback. However, what we don't see is any actual amplifiers on the market showing this behavior.

He also doesn't explain the mechanism of this increase, and if you look carefully at the referenced chart from Linsley-Hood vs. his own 'experiment', you will see that the higher-order distortion drops along with the lower-order harmonics after about 15-20dB of feedback - Pass' test stops at 15dB. I don't see why he would do that.

It also bears mentioning the work he's referencing in this article is over 30 years old.

Presumably the problem Pass identified in this article is one that's (today) easy to solve, and is apparently solved in most/all commercially available amps.

Bruno Putzey actually seems to have solved this with even more feedback , the problem with feedback has been contemporary amps in the 60-70’s did not have the open loop gain and bandwidth to take the level of feedback needed .

The purifi amps has astonishing levels of feedback but that’s due to even more complex methods I can’t even describe properly.

 

[kemmler3D]

Sorry to hear that. Some people just keep regurgitating yesterday's dogma, oblivious to the fact that they have been passed by as technology advances.

All we get from Mr. GaN is empty talk and hand waving. Putzeys put the feedback trope to rest several years ago and the objective performance of his amps has been proved many times over to be above and beyond. Yet, despite the fact that the performance is well documented both on this site and elsewhere, we continue to be bombarded with the fact less, proof less droolings of our subjectivist GaN investor. Where are the mods when you need them?

Honestly, I learned something, so in the end it wasn't a waste of time at all. It seems that the anti-feedback arguments are not very strong in today's world, but I didn't understand much about the argument until today. I still don't, but I know more than I did before. That's why we're here, right?

Bruno Putzey actually seems to have solved this with even more feedback , the problem with feedback has been contemporary amps in the 60-70’s did not have the open loop gain and bandwidth to take the level of feedback needed .

IIRC Bruno has talked about using a more robust mathematical model of the amp to improve the results of the feedback... at this point I'm far enough out of my depth to be fishing for bluefin tuna, but either way... if this additional feedback were causing audible higher-order distortion, it would be obvious in the measurements Amir does.

Pass was able to show there are drawbacks to using a bit of feedback in that article, he didn't show what happens if you use a lot of feedback. But according to the chart he put in the article, we would expect those unwanted 5th-7th harmonics to go away again.

 

[georgehifi]

we continue to be bombarded with the fact less, proof less droolings of our subjectivist GaN investor.

What I post up is for others make up their own mind/s with. Those odd ones here need to let it run it's course, instead of forcing opinions down others throats.

What I post up is for others make up their own mind/s with, this also.
And yes I did take out 5000 x $1.17shares in Feb 22 in SLX the AU mining company a few years ago, but have cashed them in at $5.70 in Feb 24 (a nice little earn), they've now dropped to $5, but they are a yoyo and they will go up again, and maybe even higher, if anyone feels they are lucky.
But it's always been a bit of a yoyo they supply the raw material to get refined in the eastern block countries then shipped EPC USA to make the patented GaN semiconductors https://epc-co.com/epc/products/publications/gan-transistors-for-efficient-power-conversion (they are not a public company yet!!) and "could be" the next Nvidia if they ever float

 

[Killingbeans]

What I post up is for others make up their own mind/s with. Those odd ones here need to let it run it's course, instead of forcing opinions down others throats.

That would be fine if you actually presented your own opinions as such. But you don't. Instead you try to push them as facts.

We are not forcing any opinons down your throat. We are just pointing out that your claims have very little chance of holding water.

Saying that people don't "have ears", if they also don't have the same subjective experience as you do, is not just an opinion. It's a bold claim. Especially considering how highly said experience is at risk of being deeply influenced by cognitive bias.

It doesn't aid anyone in making up their mind. All it does is put more fuel in the engine that keeps the FUD going.

Try presenting your claims with some solid reasoning to support them instead, and be open to getting them refuted. That way the feeling of "forced opinions" goes completely away, and we can get a healthy discussion going.

Or simply make it perfectly clear that your writings is nothing more than a personal opinion with nothing substantial to support it. That way people can rightfully ignore it completely as something useful for makeing up their minds.

 

[georgehifi]

Try presenting your claims with some solid reasoning to support them instead

They are not my claims, and I never claimed it for myself, you are delusional.
I posted up a new review of this new way of using GaN in an amp without using global feedback.

Peachtree Audio GaN 1 Gallium Nitride Power Amp Reviewed - Future Audiophile Magazine

Peachtree Audio GaN 1 Power Amp is a unique use of Gallium Nitride Class-D amps designed to work on variable output audiophile streamers

futureaudiophile.com

And then showed in the past many great designers, also have reservations of using masses of feedback .

You and goryu, spat the dummy over it, that's your prerogative.

 

[Killingbeans]

They are not my claims, and I never claimed it for myself, you are delusional.

Right... because these are definitely not claims:

If you ever A/B'd an amp that already has good low distortion and low output impedance without having to resort to masses of global feedback, just some local.
And then listened to the same amp with masses of global instead just to get those figures even a bit better again, then (if you have ears) you know what they're on about.

but it does sound very different when a little local vs a lot of global feedback is used around a well designed same amp, so long as damping factor (output impedance) is still kept reasonable, the local feedback will and does sound better, "less sterile".

But the difference in sound between little or no feedback on a well designed amp that still has good measurements vs the same one with masses of feedback is quite startling to your listening pleasure, should try it one day.

Yeah, I'm totally delusional

It's the same kind of reasoning we get when dealing with magical rocks and other products from cloud-cuckoo land. All of them will only reveal their true potential to people "with ears". All of them makes everything "less sterile". And all of them are know to have a "startling" effect if you just try them (courtesy of the placebo effect).

All I'm asking for is the results of some solid investigations into the audibility of feedback in modern well performing amplifiers. It's the only way to steer clear of fairy tales.

Audiophile gurus making vague speculations about this or that kind of distortion does not count as such.

 

[kemmler3D]

Around these parts we not only have ears, we have brains. And the brains know that the only things to trust less than your own ears are someone else's ears.

 

[georgehifi]

Around these parts we not only have ears,

Too bad the other 2 here don't have any, never a mention about how something sounds from them, even if it is a subjective comment

Nelson Pass: "Instruments only measure what they were designed to measure.” That's all they know.

 

[kemmler3D]

too bad the other 2 don't have any, never a mention about how something sounds from them, even if it is subjective

Well...

If anyone on this sorry excuse for a planet could demonstrate that there was actually something different to hear, we'd probably all go listen to it.

On this forum, most of us would be embarrassed to narrate what we hear, subjectively, knowing full well there's nothing TO hear. We're way past complimenting the emperor's new clothes, you see.

There have been standing challenges for 5 figures, (for years) where if anyone could pass a blind test between two amps operating within their rated power, they'd win the cash. Guess how many people have collected?

 

[goryu]

I think it is time to put this troll on a diet.

 

[kemmler3D]

Because you'll get verbally raped if you did.

Quite the opposite, it's because on other forums, you get attacked if you DON'T. Literally, it's in the forum rules at head-fi that you'll get banned for talking science and facts outside of the prescribed sub-forum. What a joke. A hair's breadth from flat-earth discussions.

See how long you can enjoy the sterilized sound of Bruno's Kii speakers for, I've tried a few times 1/2hr max for me.

Here's the thing - everyone is entitled to their preferences, even (especially?) at ASR. You don't have to back up your preferences with facts, you can like whatever you want. Some people here love tubes, some like Purifi amps, others are happy with Fosi, etc. Some like Kii speakers, some like LS3/a, some like KEF, some Genelec, some even like Zu. That's all fine.

The difference on this forum is if you make a claim beyond "I like this" and start saying "this is how it is", we're going to need receipts. And not hand-written ones, either.

There is a big difference between "it sounded different to me" and "it sounds different". On other forums the distinction is maybe not so meaningful, here it is.

 

[georgehifi]

Quite the opposite, it's because on other forums, you get attacked if you DON'T.

Other forums I'm in, members love both the subjective and objective, as you can draw parallels between the two, if you read between the lines especially the subjective lines.

Here's the thing - everyone is entitled to their preferences, even (especially?) at ASR.

Yeah right pull the other one, (just don't say it).